The present invention relates to a head feeding mechanism and an optical pick-up feeding mechanism, more particularly to a head feeding mechanism and an optical pick-up feeding mechanism that use a feed screw.
There is provided a feeding mechanism in which a feed screw is used for feeding an optical pick-up as a head for recording and/or reading information signals on/from an optical disk as a disk-like recording medium. FIG. 1 shows an example of such a feeding mechanism.
A feed screw a comprises a thread part b, a gear c linked to one end of the thread part b, and a receiving part d that are integrally formed. The feed screw a is rotatably supported by two bearings disposed with a certain distance therebetween in the axial direction of the feed screw.
In the feed screw a, one end of the thread part b provided with the gear c and the receiving part d is supported by a bearing e and the other end of the thread part b, at which neither gear c nor receiving part d is formed, is supported by an unillustrated thrust bearing. The gear c is linked to a motor via an unillustrated intermediate gear. The receiving part d is put in contact elastically with an elastic body f. Thus, the feed screw a is pressed by a force F2 shown in FIG. 1 in the axial direction.
One side of the bearing e is opened so as to mount the feed screw a. On the opening side of the bearing e is attached with a holding member g used to prevent the feed screw a from falling.
Consequently, the feed screw a is engaged with an unillustrated feed nut provided in the base of an optical pick-up, so that the optical pick-up is moved in the radial direction of the optical disk due to the rotation of the feed screw a driven by a motor.
In the feeding mechanism shown in FIG. 1, clearances .DELTA.x1 and .DELTA.x2 necessary for allowing the free rotation of the feed screw a are provided between the feed screw a and the bearing e.
These clearances .DELTA.x1 and .DELTA.x2 cause the feed screw a to generate an excessive play in the C direction shown in FIG. 1 when the feed screw a rotates. This further causes collision between the feed screw a and the bearing e, which results in generation of vibration in the feeding mechanism. This generated vibration, when transmitted to the optical pick-up, disables the optional pick-up to read signals recorded on the optical disk. When the vibration is large, track-jumps will occur, causing sound skipping.
In order to solve such the troubles, a measure may be taken to determine the dimensions of the feed screw a and the bearing e for minimizing the clearances .DELTA.x1 and .DELTA.x2. This measure, however, leads to other problems; dimensions of those parts must be managed more strictly and friction loss due to the rotation (load) of the feed screw a and the bearing e is increased.
Especially, in the case that the bearing e and the holding member g provided on the opening side of the bearing e are formed with different members as described above, it is very difficult to minimize the clearances .DELTA.x1 and .DELTA.x2 because of the influence of the summation of the dimensional tolerances of those members.